It is known to prepare isothiocyanates by oxidizing N-monosubstituted dithiocarbamates with concentrated hydrogen peroxide, see German Pat. No. 2,105,473 and related Giesselmann U.S. Pat. 3,787,472. According to this process there are obtained alkylisothiocyanic acid esters in a purity of 98% and in high yields. However, important disadvantages of this process are that only alkyl derivatives are accessible and that relatively high hydrogen peroxide concentrations must be used.
Furthermore, it is known to produce isothiocyanates by reaction of N-monosubstituted dithiocarbamates with cyanogen chloride in aqueous solution, see Claudin U.S. Pat. No. 2,338,902. However, according to this process the lower alkyl isothiocyanates can only be obtained in yields of about 65 to 70%. Besides, as byproducts considerable amounts of water insoluble thiocyanogen compounds are formed which increased the difficulty of the working up process.
It is the objective of the invention to develop a new process for producing isothiocyanates which do not have the above stated disadvantages.